1. Field of the Invention
The present invention relates to a fuel gauge for vehicles, and more particularly to a fuel gauge in which an indication for residual quantity of fuel contained in a fuel tank when an ignition switch was turned off to stop an engine is not different from an indication for residual quantity of fuel contained in the tank when the ignition switch is turned on to start the engine after a while.
2. Description of the Prior Art
Heretofore, needle type fuel have been used to indicate the amount of fuel contained in a fuel tank of a vehicle. Recently, there is however a tendency that a digital fuel gauges have been employed using an electronic circuit is used.
When the engine of a vehicle is rotated, the temperature of the fuel in the fuel tank rises due to heat of the engine, thereby evaporating a portion of fuel, so that the vapor pressure is enhanced and the internal pressure in the fuel tank is increased. Consequently, the fuel tank is deformed to increase the capacity of the fuel tank and the surface level of fuel in the tank is lowered. However, when the engine is stopped, the capacity of the fuel tank is reduced and the surface level of fuel in the tank tends to increase, since the temperature of fuel in the tank is decreased, and the vapor pressure is lower as compared with the surface level of fuel in the tank at the time when the engine is operated or for a while after a engine is stopped. Therefore, since a position of a float of a fuel sensor is somewhat different between the time when the engine is operated and the time when a driver gets in the vehicle after the engine is stopped for a long time, the indication for residual quantity of fuel contained in the tank is different.